A fully automated method for the specific assessment of oestriol-16-glucuronide in urine is described. "On-line" sample preparation, including enrichment, pre-purification, focusing and injection, is combined with automated high-performance liquid chromatographic separation and fluorimetric quantification. Losses of oestriol-16-glucuronide throughout the total procedure are negligible. Thus, external calibration is feasible for quantification. Coefficients of variation are 4.44% (n = 12) for intra- and 7.85% (n = 9) for interassay variability. Assay sensitivity is 430 nmol/l. The excretion rates of oestriol-16-glucuronide relative to creatinine were estimated in 85 pregnancy urines. These oestriol-16-glucuronide estimates correlated well with those of total urinary oestriol, determined by high-performance liquid chromatography after acid hydrolysis (r = 0.957). The reference ranges of oestriol-16-glucuronide for the different weeks of gestation were evaluated. Unlike the determination of total oestriol, the present method does not need an hydrolysis step. The method is therefore well suited for the biochemical monitoring of fetal well-being under emergency conditions.